The invention relates to piston engine balancing.
Most piston driven engines have pistons that are attached to offset portions of a crankshaft such that as the pistons are moved in a reciprocal direction transverse to the axis of the crankshaft, the crankshaft will rotate.
U.S. Pat. No. 5,535,709, defines an engine with a double ended piston that is attached to a crankshaft with an off set portion. A lever attached between the piston and the crankshaft is restrained in a fulcrum regulator to provide the rotating motion to the crankshaft.
U.S. Pat. No. 4,011,842, defines a four cylinder piston engine that utilizes two double ended pistons connected to a T-shaped connecting member that causes a crankshaft to rotate. The T-shaped connecting member is attached at each of the T-cross arm to a double ended piston. A centrally located point on the T-cross arm is rotatably attached to a fixed point, and the bottom of the T is rotatably attached to a crank pin which is connected to the crankshaft by a crankthrow which includes a counter weight.
In each of the above examples, double ended pistons are used that drive a crankshaft that has an axis transverse to the axis of the pistons.
According to the invention, a piston assembly includes first and second pistons, e.g., double-ended pistons or single-ended pistons with guide rods, a transition arm coupled to each of the pistons, and a rotating member rotating in a first direction. The transition arm includes a drive member coupled to the rotating member off-axis of the rotating member. A first counterbalance is mounted to rotate in the first direction, and a second counterbalance is mounted to rotate in a second direction opposite the first direction.
Embodiments of this aspect of the invention may include one or more of the following features.
The first and second double ended pistons are arranged for reciprocating motion in a common plane. The first counterbalance is coupled to the rotating member opposite the drive member coupling. The rotating member rotates about a first axis, and the second counterbalance rotates about a second axis offset and parallel to the first axis.
A first gear is mounted to rotate in the first direction about the first axis, and a second gear is driven by the first gear to rotate about the second axis in the second direction.
In certain illustrated embodiments, the rotating member, the first counterbalance, and the second counterbalance rotate about a first axis. A first gear is mounted to rotate in the first direction about the first axis, and a second gear is driven by the first gear to rotate in the second direction about a second axis offset and parallel to the first axis.
A first pulley is driven to rotate by the second gear in the second direction, and a second pulley is coupled to the first pulley and driven by the first pulley to rotate in the second direction about the first axis. The second counterbalance is driven by the second pulley.
A third counterbalance is coupled to the rotating member opposite the drive member coupling.
In further illustrated embodiments, a third counterbalance is mounted to rotate in the first direction, and a fourth counterbalance is mounted to rotate in the second direction. The rotating member and the first, second, third and fourth counterbalances rotate about a first axis. The first and third counterbalances are oriented 180 degrees apart relative to the first axis, and the second and fourth counterbalances are oriented 180 degrees apart relative to the first axis. The first and fourth counterbalances are both oriented in a first direction relative to the first axis, and the second and third counterbalances are both oriented in a second direction relative to the firs axis, the second direction being 180 degrees from the first direction.
A first gear is mounted to rotate in the first direction about the first axis, and a second gear is driven by the first gear to rotate in the second direction about a second axis offset and parallel to the first axis. A first pulley is driven to rotate by the second gear in the second direction, and a second pulley is coupled to the first pulley and driven by the first pulley to rotate in the second direction about the first axis. The second and fourth counterbalances are driven by the second pulley.
A fifth counterbalance is coupled to the rotating member opposite the drive member coupling, and the second counterbalance is integrated with the fifth counterbalance.
According to another aspect of the invention, a piston assembly includes at least three equally spaced members. Two of the members are pistons. A transition arm is coupled to each of the members. The transition arm includes a drive member coupled to a rotating member off-axis of the rotating member. The rotating member rotates in a first direction. A first counterbalance is mounted to rotate in the first direction, and a second counterbalance is mounted to rotate in the first direction.
Embodiments of this aspect of the invention may include one or more of the following features.
A fourth member is coupled to the transition arm. The four members are equally spaced about the transition arm with a first of the two piston being positioned opposite a second of the two pistons. A third counterbalance is coupled to the rotating member opposite the drive member coupling. The pistons are double-ended pistons or single ended pistons with guide rods.
According to another aspect of the invention, a piston assembly includes at least three equally spaced members. Two of the members are pistons. A transition arm is coupled to each of the pistons. The transition arm includes a drive member coupled to a rotating member off-axis of the rotating member. The rotating member rotates in a first direction. A counterbalance is mounted to rotate in the first direction. The counterbalance is positioned axially aligned with and spaced from the rotating member.
Embodiments of this aspect of the invention may include one or more of the following features.
A fourth member is coupled to the transition arm. The four members are equally spaced about the transition arm with a first of the two piston being positioned opposite a second of the two pistons. The pistons are double-ended pistons or single ended pistons with guide rods.
According to another aspect of the invention, a method of counterbalancing a piston assembly including first and second double-ended pistons, a transition arm coupled to each of the pistons, and a rotating member rotating in a first direction, the transition arm including a drive member coupled to the rotating member off-axis of the rotating member, includes mounting a first counterbalance to the piston assembly to rotate in the first direction, and mounting a second counterbalance to the piston assembly to rotate in a second direction opposite the first direction.
According to another aspect of the invention, a piston assembly includes at least two pistons and a transition arm coupled to each of the pistons. The transition arm including a drive member with a spherical portion. The spherical portion couples the drive member to a rotating member off-axis of the rotating member.
Embodiments of this aspect of the invention may include one or more of the following features.
The rotating member includes a counterbalance. The drive member includes a cylindrical end portion. The rotating member includes a flywheel, and the counterbalance is mounted to the flywheel. The flywheel defines a cylindrical opening for receiving the cylindrical end portion of the drive member, and the counterbalance defines a spherical opening for receiving the spherical end portion of the drive member.
Advantages of the invention include limiting vibration of the piston assembly. The invention greatly reduces vibration of the engine, due to internal canceling of vibrating forces and couples. A balanced machine has greatly reduced forces on its bearings and mounting hardware. The bearing life may be extended many times, and lighter parts and mounts can be used, if the vibrational forces and couples have been reduced by balancing. Another advantage achieved by balancing is the ability to run smoothly at higher speeds. Since this balancing method nearly completely compensates for rotating and inertial imbalance, the engine can be run at higher speeds. Imbalance forces that are not compensated increase as the square of the speed and quickly become a limiting factor as speeds increase. In many engine applications, the trend is toward higher speeds, placing more importance on the better balancing methods available with the invention.
Other features and advantages of the invention will be apparent from the following description and from the claims.